itself. Such a machine is useful and expeditious, if the work be
not too heavy, and is illustrated in Fig. 776 by an example from
London Bros, of Johnstone, N.B. Some makers use two lifting
screws when doing heavy work, and others support the boring bar
on the saddle, as in Fig. 249, p. 237; but the main characteristics
remain, such as deep bed and short length, and the movement of
the work itself for feed.
Class 3, with fixed "work, is well described on p, 161.
„ The fourth class, the vertical machine, has already been men-
tioned, and its advantages, truth of surface for large diameters,
explained. The general design is shewn in Fig. 777, the con-
struction being similar to those of Class 3, where the work is fixed
and the tool fed along the bar hy an epicyclic train of wheels at
the upper end. Of course, the bar must be lifted vertically when
removing the work, but there is less risk of accident than with
the horizontal machine.
The snout-boring machine, Fig. 778, is made by Messrs. J.
Buckton & Co., for cases where a bar cannot be passed through
the work. "Very large diameters cannot well be done, but most
hydraulic cylinders can be conveniently bored. The driving is
by worm gearing, and the feed is given to the saddle on which
the work is bolted, lathe fashion. A facing head is also supplied.
JP. 268. The Slot-drilling Machine.—Fig. 779 shews one
of these useful machines, to Messrs. Buckton's design. It is
driven by speed cones A., from a countershaft in order to make